1. Field
The disclosed embodiments relate to techniques for improving safety in rechargeable lithium-polymer battery cells. More specifically, the disclosed embodiments relate to the design of a pressure-relief mechanism which improves the safety in lithium-polymer battery cells.
2. Related Art
Rechargeable batteries are presently used to provide power to a wide variety of portable electronic devices, including laptop computers, cell phones, PDAs, digital music players and cordless power tools. The most commonly used type of rechargeable battery is a lithium battery, which can include a lithium-ion or a lithium-polymer battery.
A potential safety issue can arise if there is a gas buildup within a rechargeable lithium battery cell. This can occur, for example, if the cell is overcharged, if there is a short within the cell, or if the cell is left uncharged for a significant period of time. This type of gas buildup can potentially cause the battery cell to swell or even to explode, which can seriously damage the portable electronic device, and may even start a fire.
To alleviate this problem, cylindrical lithium-ion battery cells are often equipped with a vent valve to release the internal pressure in the battery cell when a gas buildup occurs. However, there exist no comparable pressure-relief mechanisms for lithium-polymer batteries, which are becoming increasingly popular in portable electronic devices. A lithium-polymer battery is typically enclosed in a flexible pouch, which is lightweight and inexpensive to manufacture. However, no pressure-relief mechanism has been developed for these pouches so far.